If a train company back in 1850 had a near monopoly in the whole country or a whole state and decided who could or not use their "platform" based on what they s

If a train company back in 1850 had a near monopoly in the whole country or a whole state and decided who could or not use their "platform" based on what they say, would it be alright? They sale ads. If no advertiser wants to put an ad on a website, fine. But they can't decide to not offer their service.